Frictional Force on Car Tires Rounding a Curve

We know that $F_{\text{c}}=m\frac{v^2}{r}$ . Therefore,

The image above shows the forces acting on the car while rounding the curve. In this diagram, the car is traveling into the page as shown and is turning to the left. Friction acts toward the left, accelerating the car toward the center of the curve. Because friction is the only horizontal force acting on the car, it provides all of the centripetal force in this case. Therefore, the force of friction is the centripetal force in this situation and points toward the center of the curve.

If the car is about to slip, the static friction is at its maximum value and $f={\mu }_s\text{N}={\mu }_{s}mg$. Solving for ${\mu }_s$, we get ${\mu }_s=\frac{938}{900\times 9.8}=0.11$. Regardless of whether we know the maximum allowable speed for rounding the curve, we can conclude this is a minimum value for the coefficient.